For all intents and purposes, they are the game gun except for barrel length and what they come with for priming systems. The Bighorn comes with both the 209 system as well as the breech plug for percussion or musket cap ignition. You choose what nipple for either the percussion or musket cap. Other differences might be camo patterns, blued vs. stainless barrels etc.
The Wolverine that comes marked 209 is indeed a 209 ignition system, which is not legal in Washington. However all one has to do is search online for a Knight #90023 breech plug and simply take out the 209 breech plug that came with the Wolverine and screw in the new one which accepts percussion or musket caps according again to nipple choice that you make.
I have both models and that information is directly from Knight as I talked with them on the phone. All parts between the Bighorn and Wolverine interchange...i.e. barrels, stocks etc. Hope that help.